<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
<script>
// console.log(Number(null));--0
// console.log(Number(undefined));--NaN

console.log(typeof null);
console.log(typeof [1,2]);
// var str1='123';
// var str2='123';
// console.log(str1===str2);
// var arr1=[];
// var arr2=[];
// console.log(typeof arr1,arr1===arr2);

function fIsType(type){
    // if(typeof type=='object'){
    //     return '数组';
    // }
    if(type instanceof Array){
        return '数组';
    }else if(type instanceof Object){
        return '对象';
    }

}
console.log(fIsType([1,2,3]))

console.log(null instanceof Object );
</script>
</body>
</html>